In U.S. Pat. No. 4,938,108 to the present inventor, the contents of which being hereby incorporated by reference (hereinafter referred to as “the Prior Patent”), there has been disclosed a theft resistant fastener system which included a rotatable wrench adapted to engage the head portion of the fastener. The wrench and fastener comprised at least three ball-and-socket joints distributed about the fastener axis. Each of these ball-and-socket joints included a ball in the wrench and a socket in the head portion of the fastener, with each socket being provided with a circular cross-section about a socket axis extending at an acute angle to the fastener axis. The wrench comprised a releasable actuator for pressing the balls into respective sockets preparatory to and during rotation of the wrench about the fastener axis. For preventing the clearing the balls from the head while being pressed into the sockets, the head portion at each socket was formed with an overhang extending over part of the ball. The need for auxiliary means for biasing the balls out of the sockets upon release of the actuator has been avoided by providing each overhang with an outer limit closer to the fastener axis than a center of the corresponding one of the balls of the ball-and-socket joints. Actuation of the fastener by a conventional wrench was prevented by providing the head portion with outward extending slopes at the sockets and otherwise about the fastener axis.
Certain limitations of the Prior Patent system have led the present inventor to further develop the conceptual approach therein disclosed. The main limitation relates to the holding or gripping method of the balls by the wrench. As clearly seen and described, the balls are enclosed within sockets formed in the wrench actuator. In order to prevent the balls from free-falling out of their sockets (during non-use of the wrench) it is mandatory to provide a circumferential barrier—whether continuous or at least at three equally distanced locations (“overhang” or “edges” 84 in FIGS. 2A, 2B of the Prior Patent). The fulfillment of this condition dictated that the exposed, “active” portion of each ball be less than half, and practically only about one third.
This inevitable requirement has caused the following drawbacks: It has limited the amount of torque that could be applied by the wrench depending on the strength of the material (metal) of which the bolt has made; and, it has set a limit to the miniaturization degree of the tool. For example, bolts of, say, 3 mm diameter are ruled-out in as much as the Prior Patent system is concerned.
From another aspect, although derived from the above, the Prior Patent system is properly applicable with regard to dome-shaped (semi-spherical or round cap) bolts. This is due to the fact that in order to assure smooth, unimpeded release of the balls from the bolt head sockets back into the wrench sockets, both must be aligned, and the common axis thereof (designated 352 in FIG. 2A of the Prior Patent) must be inclined at an acute angle relative to the bolt axial axis. Therefore, bolts other than of round cap bolts (or nuts) such as PAN bolts or countersunk (flat-headed) bolts were unsuitable to be handled by the Prior Patent wrench system.
It is therefore the general object of the invention to overcome the above listed and other deficiencies of the Prior Patent system, while still maintaining the outstanding advantages thereof.
It is a further object of the invention to substitute the balls configuration by one that will enable enhanced torque transmission capabilities.